1. Field of the Invention
This invention relates to a diagnostic device used in an electronic control unit adapted to control a plurality of driven loads in accordance with input signals from a plurality of sensors, particularly applicable to engine analysis in an automotive vehicle.
2. Description of the Related Art
In conventional diagnostic devices of this type, which are used in electronic vehicle-control units, diagnosis is effected, either while the vehicle is running or at rest, by detecting abnormal outputs due to short-circuiting or disconnection of various sensors mounted on the vehicle. An example of such an electronic control unit, mounted on a vehicle and equipped with a diagnostic function is disclosed in U.S. Patent Ser. No. 160,837 now U.S. Pat. No. 4,924,391, which corresponds, for example, to Japanese Utility Model Laid-Opens No. 63-135437 and 63-135252, and to Japanese Patent Laid-Open No. 63-243832.
The problem with such conventional diagnostic devices is that they can only diagnose trouble with sensors: they cannot detect trouble in loads which are not equipped with sensors.